US1977156A - Electric heater and thermostat - Google Patents

Description

Get. 16, 1934. R STALEY 1,977,156

ELECTRIC HEATER AND THERMOSTAT Filed Dec. 1, 1930 2 Sheets-Sheet l 'mwmw NVENTOR A TTORNE Y Oct. 16, 1934. R. u. STALEY ELECTRIC HEATER AND THERMOSTAT Filed D90. 1, 1930 2 Sheets-Sheet 2 a v fi//////// 0 I INVENTOR U: M H mp Patented Oct. 16, 1934 UNITED STATES- PATENT OFFICE 14 Claims.

My invention relates to electric fluid heaters wherein the electric heating element is in direct contact with the fluid, the heating of which causes the same to circulate through the heater.

The principal object of the invention is to provide a device of the class described that is simple, compact and accessible in construction, and reliable and efficient in operation.

Another object is to provide an electric fluid heater wherein the temperature of the fluid entering the device will automatically control the flow of current to the heating element.

A further object is to provide an electric fluid heater embodying an automatically controlled electric switch which is subject also to manual control.

A further object is to provide an electric fluid heater, of the direct contact type wherein the leakage of current to the metal housing thereof, under unfavorable operating conditions, is greatly reduced.

A still further object is to provide an electric fluid heater of the direct contact type that is adapted to reduce the injurious effects of leakage current between the heating element and housing under unfavorable operating conditions.

With the above and related objects in View, the invention consists of certain parts and combination of parts hereinafter described, illustrated in. the accompanying drawings and embraced in the appended claims.

In the drawings, Fig. 1 is a sectional elevation of a fluid heater constructed in accordance with the invention with the bottom closure plate removed.

Fig.2 is a sectional elevation through the housing and liner on line A-A of Fig. 1, disclosing an elevation of the heating element assembly.

Fig. 3 is a bottom view of the heater.

Fig. 4 is a transverse section through the intake pipe on line BB of Fig. 1.

Fig. 5. is a transverse section through the body of the heater on. line C-C of Fig. 1.

Fig. 6 is a diagram of the electrical connection usually employed.

Referring. to the drawings, throughout which like reference numerals indicate like parts, the numeral 7 refers to a one piece housing, preferably of aluminum, providing a lower switch comp'artment and an adjacent. upper fluid compartment into which fluid inlet pipe 8 and outlet pipe 9' are screwed, said pipes serving also to support the heater. The upper body portion of the housing is circular in section, as shown in Fig. 5 and the lower portion thereof is octagonal in section and of thicker metal as shown in Fig. 4.

An insulating liner l0, corresponding in sectional shape to the housing and preferably of glazed porcelain, is'notched opposite the intake opening as at 10 and is provided with an inward- 1y projecting perforated neck and deflector head 10". The liner is made a loose fit in housing to allow for inequalities in expansion and contraction. The alignment of notched opening 10 with the intake opening is assured by the octagonal shape of the lower main portion of the housing and the skirt portion of the liner. The flat faces of the octagonal portion also are desirable for holding the heater in a vice or other clamp during the process of manufacture or while making adjustments or repairs.

The bottom of the housing is closed by means of a heavy porcelain base 11, which mounts integral therewith, a hollow porcelain core having a lower portion of elliptical section adjacent the base, as shown in Fig. 4, and an upper portion providing a plurality of notched longitudinal ribs, as shown in Figs. 2 and 5. A resilient gasket 12, of suitable material, is placed between the porcelain base and case, and a gasket 13 of similar material is placed between the base and clamp ring 14 which coacts with screws 15 to removably secure the base to the housing. The gaskets assure a fluid tight joint and serve to equalize the stresses in the pocelain base due to the tension of the screws and pressure of the liquid inside the housing.

A metallic shield 16 corresponding in shape to the top plan of the porcelain core and having an aperture 16 in a downwardly projecting fin, is inserted in the top of said core with said aperture 16 opposite the notches 11 at the top of the core. Coiled heating element 17 is passed through aperture 16 and notches 11' until the mid point of the coil is in contact with the shield fin and is then wrapped in double spiral around the core in the notches provided in the longitudinal ribs thereof as shown clearly in Fig. 2.

The pitch between successive turns of the double spiral preferably diminishes from the ends of the coiled heating element upward toward the top of the core to conform somewhat to the diminuti'on in the electrical difference in potential between the turns of the spiral. The uncoiled ends 17' of the heating element are doubled back to provide greater conductivity andare passed through apertures 11" in the porcelain base and appended core. Apertures 11" are then sealed with a suitable heat resisting and non-hygroscopic cement 18, thus completing the assembly of the heating element unit.

The flow of current to the heating element is controlled by means of a double pole switch mounted below the porcelain base on studs 19, the upper ends of which are cemented in holes provided therefor in the base. The movable contacts 26 of the switch are mounted on a light but rigid bar 21 of suitable. insulating material provided near the ends thereof with aluminum sleeves 22 for slidably mounting on studs 19. The switch contacts are made of non-fusing contact material, but nuts 23 and cup washer 24, which are used to secure the contacts in position and to make connection with flexible connecting loops 25, are preferably made of an aluminum alloy in order to reduce the weight of the moving parts. The other ends of connecting loops 25 are connected to the looped ends of the heating element, preferably by brazing. Fixed contacts 25 are mount- .ed on abar of heavy insulating material 21 by means of brass nuts 23, which in combination with copper cup washer 24' also form the terminals for connection with the supply wires, not shown. Bar 21' is mounted on studs 19 by means of nuts 25, which provide a readily accessible and convenient means for adjusting the travel of the movable contacts, and for compensating for the unavoidable wear thereof. A tapped hole 27 is provided in the skirt of the housing to receive a suitable terminal fitting for the conduit or armoring for the circuit wires, neither of which are shown as they are standard practice in the art.

The switch may be actuated automatically by means of a thermostat element having a tubular body 28, tapering fiat tubular pressure loop 26, and mechanism bar 29, all securely assembled, preferably by brazing. The interior space of the thermostat is filled with a fluid having a high temperature coefficient of expansion, such as ether. This fluid is introduced through the threaded hole 30 in the head 28 of the tubular body, after which screw 31 is inserted and the head tightened against gasket washer 32. The tubular body is adapted to project through an axial aperture in the porcelain base into the space within the heater core, and is secured therein by means of the cement filling 18'.

Two side frames 33 are fixedly secured to bar 29 in spaced apart relation and are provided with holes 34 adapted to receive pins 35, on which are mounted single Y lever 36, single spring bar 37 and double spring bars 38 in the relation seen best in Fig. l. Pins 39 passing through the ends of the spring bars and carrying spacers 40, are adapted to hold the looped ends of tension springs 41, which are free to work clear of side pieces 33. A pair of links 42 and pins '43 serve to connect the end of Y lever 36 and the end of pressure loop 28, and a single link 44 and pins 39 and 45 serve to connect the ends of spring bars 38 to a pair of angle lugs 46 which are secured, as by riveting, to movable bar 21. Bar 33 provides a stop for the Y lever.

The lower ends of side frames 33 are closed by means of a U shaped piece 47 and secured thereto, preferably by brazing, to form a spring cupto receive helical spring 48 and spring head 49, slidably mounted therein. Thermostat control lever is mounted in operative relation to spring head 49 by means of pin 51, and is adapted to engage the spring head alternately in notches 52 and 52, when actuated manually by means of insulating handle 53, screwed onto the threaded end 50' which is positioned between, but not touching, links 42.

The strength of spring 48 and the arrangement of spring head 49 and notch 52 is such that when lever 50 is in the lower position, as illustrated in the drawings, the strength of pressure loop 28 is not sufiicient to move the control lever to its upper position so long as the fluid surrounding thermostat body 28 is not below a predetermined temperature, preferably .about five degrees Fahrenheit above the freezing point of the fluid. Hence for all usual operating temperatures, when the control lever is in the lower position the switch contacts are held open and the thermostat element is rendered inoperative. In case the temperature of the fluid in the heater falls below the predetermined temperature for which the device is adjusted, the contraction force of loop 28 becomes sufficient to move lever 50 to the upper position whereby spring head 49 engages notch 52, and in-so doing the pressure loop actuates the appended mechanism to close the switch, as hereinafter described, thus energizing the heating element, raising the temperature of the fluid and preventing the destruction of the heater in freezing weather.

The space containing the thermostat mecha nism is closed by cover plate 54 which is removably secured to the skirt, of housing 7 by means of screws 55. Aperture 54' in the cover plate provides an emergency drain for the switch compartment.

By removing handle 53 and coverplate 54, disconnecting the supply wires and removing screws 15, the complete operating unit may be readily removed from the housing for inspection, adjustment and repairs, thus greatly reducing the time usually required for this important work.

The heater of my invention may be used in many ways for the heating of various liquids. It is particularly adapted to heating water for residential and industrial purposes. When so used, inlet pipe 8 is connected with the bottom of a storage tank, not shown, and outlet pipe 9 is connected with the top ofthe tank, The water obviously comes into contact with heating element 17 which imparts the heat generated therein directly to the water. 1 I

Only alternating current, which may be supplied by a transformer having primary and sec ondary windings 49 and 49" respectively is suitable for the operation of the heater. It is standard practice in the art to ground the neutral or mid-point of transformer secondary 49', as in dicated diagrammatically in Fig. 6, thus making the use of a double pole switch imperative for the control of a heater of this type. The heater is placed in operation by manually raising handle 53 and appended control lever '50 to the upper position, thereby moving control lever 50 upward beyond the range of movement of the end of pressure loop 28 where it is held by means of spring head 49 in notch 52'. When the'water is cold, pressure loop 28' actuates lever 36 to force the end of spring bar 37 downward, thus further tensioning the springs 41 until they pass pin 35, whereupon they in turn pull lever 38 and appended movable switch contacts to their lower or closed position, against. the stationary contacts, with a quick snapping movement. This movement is accentuated by virtue of the opening between the jaws of the Y lever, which permits the end of spring bar 37 tosnap against the lower fork, thus increasing the effectiveness of the spring tension for the closing operation.

When the switch contacts'are closed, the heating element is connected electrically to the transformer.

As the water in the heater is raised. in'temperature, it expands and rises through discharge pipe 9 to flow into the topof the storage tank. While cold water from the bottom. of the tank flows into the heater and is deflected downward-against the top of base'll by means of. inverted U shaped projection 56 of the porcelain core. Projection 56 serves also to direct the infiowing water through apertures 57' so as to effectively surround the interior projection of thermostat body 28. It will be noted that the interior construction of the heater is such that the water is free to contact the heating element throughout its entire coiled length, except whereit issupported by the notches in the ribs of core ll, thus increasing its heating ei'ficiency and preventing the accumulation of sedimentary deposit, which tends to insulate the heating element from. the water and cause the same to burn out. Furthermore, by directing the flow of incoming water through apertures 57, sediment is prevented from accurnulating around the body of the thermostat. By terminating the heating element at a considerable distance above the base and protecting the uncoiled ends thereof, as clearly illustrated in Fig. 2, it is necessary for the sediment to build up to the heating element before it can interfere with the operation of the device. But the flow of water through restricted areas 57' tends to reduce this building upof the sediment directly under the ends of the heating element.

With handle 53 raised to its upper position and the switch closed, the heater will continue to heat the water in the tank until all of it is heated, then the infiowing hot water recirculating through the heater will cause the ether in the thermostat element to expand and extend pressure loop 28, thereby moving the end of spring bar 37 upward through the intermediacy of links 42 and Y lever 36, thus further tensioning springs 41 and moving them upward until they pass pin 35 whereupon they pull levers 38 and appended movable switch contacts to their upper or open position with a, quick snapping movement, thus minimizing any tendency for arcing at the contacts. By with.- drawing a sufficient quantity of hot water from the tank, or allowing the heated water to cool, the other in the thermostat element contracts thus allowing the pressure loop to contract and close the switch contacts with a similar quick snapping movement, thus again energizing the heater until the tank is again filled with hot water. The heater thus tends to. automatically maintain a nearly full tank of hot water as long as handle 53 is in its upper position.

The operation of the heater maybe stopped at any time by manually hoving handle 53' to its lower position, thus pulling the end of the pressure loop downward, which, in turn actuates the balance of the mechanism to snap the switch upward to its open position, as previously described. In this way the heater may be made. to meet occasional and light demands for hot water as well as to automatically maintain a nearly full tank of hot water to meet maximum demands.

No appreciable leakage current from. the heating element to the housing can be detectedlunder the normal operating conditions hereinbefore described, even with insulating liner l0 removed from the housing.

But incase a mistake is made in connecting the heater to the source, or to a transformer having other than its neutral point grounded, these ideal conditions cannot exist and the heating element maysoon be destroyed by electrolytic action.

For" instance, incase a single pole auxiliary switch 60,. shown by dotted lines in Fig. 6, is installed for the remote control of the heater, current would: continue to flow after the switch was opened, through conductor 58 to heating element 17, thence through the water, particularly that filling the openings. in. liner 10, to the housing and connected piping, thence to, and through, the ground to conductor 59 andback to the mid point of transformer secondary winding 49", thus forming a complete circuit of high resistance operating at one half normal voltage. Under such conditionsit is desirable that the leakage current from the heating element to the housing and connect ing pipes shall be a minimum in order to minimize the wasting away of the heating element, due to electrolysis. To this end I use projection 51 of the core and the perforated neck and deflector head 10" of the porcelain liner to increase the length. of the leakage paths thus increasing their resistance. What leakage does occur is mostly between aluminum housing 7 and shield 16, which serves as an electrolysis guard for the heating element, and provide for the production, principally, of harmless aluminum salts as the result of what little electrolysis does occur. This obviously is an abnormal operating condition, but when such a misapplication is made, the heating element is well protected.

My invention is not necessarily limited to the details shown and described in this specification as the invention may be embodied in various other forms, by those skilled in the art, without departing from the spirit and intent thereof which I have set forth in the appended claims as new and desire to secure by Letters Patent of the United States.

Having thus described my invention what I claim is:

1. In an electric fluid heater, a housing providing a fluid compartment having inlet and outlet openings, an insulating base closing said fluid compartment, an insulating core projecting from said base within said fluid compartment, a coiled heating element wound in double spiral about and with corresponding portions thereof on opposite sides of said core and terminating in uncoiled connection. leads, apertures through said base for said connection leads, and means for sealing said leads in said apertures.

2. In an electric fluid heater, 2, housing providing a. fluid compartment having inlet and outlet openings, an insulating base closing said fluid compartment, an insulating core projecting from said base within said fluid compartment, a plurality of notched longitudinal ribs peripherally of said core, a coiled heating element wound in double spiral about and with corresponding portions thereof on opposite sides of said core in said notches and terminating in uncoiled connection leads, apertures through said base for said connection leads, and means for sealing said leads in said apertures.

3. In an electricfluid heater, a housing providing a fluid compartment having inlet and outlet openings, an insulating base closing said fluid compartment, an insulating core projecting from said base within said fluid compartment having an elliptical section adjacent and extending a substantial distance from said base and a plurality of longitudinal ribs peripherally of the remainder of said core, a plurality of notches in said ribs, a coiled heating element wound in double spiral about said core and terminating in uncoiled connection leads, said base and the end portions of the elliptical section of said core having apertures for said connection leads, and means for sealing said leads in said apertures.

4. In an electric fluid heater, a housing providing a fluid compartment having inlet and outlet openings, an insulating lining for said fluid compartment, an insulating base closing said fluid compartment, an insulating core projecting from said base within said fluid compartment, a coiled heating element wound in double spiral about and with corresponding portions thereof on opposite sides of said core and terminating in uncoiled connection leads,-said base having apertures extending therethrough for said connection leads and means for sealing said leads in ,said apertures.

5. In an electric fluid heater, a housing providing a switch compartment and an adjacent fluid compartment having inlet and outlet openings, an insulating base closing said fluid com partment, an insulating core projecting from said base within said fluid compartment, a coiled heating element wound in double spiral about and with corresponding portions thereof on opposite sides of said core and terminating in uncoiled connection leads, said base having apertures therethrough for said connecting leads, means for sealing said leads in said apertures, a control switch having fixed and movable contacts in said switch compartment mounted on said base, flexible loops connecting said leads with said movable contacts and means for actuating the movable contacts of said switch.

6. In an electric fluid heater, a housing providing a switch compartment and an adjacent fluid compartment having inlet and outlet openings, an insulating base closing said fluid com-1- partment, an insulating core projecting from said base within said fluid compartment, a coiled heating elementwound in double spiral about and with corresponding portions thereof on opposite sides of said core and terminating in uncoiled connection leads, said base having apertures base, flexible loops connecting said leads with said movable contacts and thermostat means within said fluid compartment mounted in said base and adapted automatically to close the contacts of said switch when the inflowing fluid is cold and adapted to open said contacts when the inflowing fluid is hot. i

7. In an electric fluid heater embracing a metal housing having inlet and outlet openings and a bare heating element in direct contact with the fluid, means reducing the leakage of current between the heating element and the housing under unfavorable operating conditions, comprising in combination an insulating lining for said housing, an insulating base closing said housing, an insulating core projecting from said base within said housing and supporting said heating element and means incorporated with said core and with said lining for increasing the resistance of the leakage paths between said inlet and outlet openings and said heating element.

,8. In an electric fluid heater the combination of a metal housing having inlet and outlet openings, and an insulating liner for said housing a bare metallic heating element in direct contact with the fluid, an electrolysis guard protecting said heating element comprising a metallic shield positioned between said heating element and said housing in'the principal path of current leakage between the same, and means electrically connecting said shield with said heating element.

9. In a direct contact electric fluid heater, an insulating member comprising a base, a core having an enlarged portion adjacent and projecting a substantial distance from said base, a plurality of longitudinal ribs peripherally of the remainder of said core, a plurality of notches in said ribs arranged in a series of diminishing space distances outwardly of said core and adapted to support a coiled heating element wound in double spiral about and with corresponding portions thereof on opposite'sides of said core, and apertures through said base and the enlarged portion of said core for the connection leads of said heating element.

10. In a direct contact electric fluid heater, an insulating base, an insulating core having an enlarged portion adjacent and projecting a substantial distance from said base, a plurality of notched longitudinal ribs peripherally of the remainder of said core, a coiled heating element wound in double spiral about and with corresponding portions thereof on opposite sides of said core in the notches of said ribs with outwardly diminishing pitch distances between the adjacent turns of said spiral and terminating in connection leads, apertures through said base and the enlarged portion of said core, and means for sealing said leads in said apertures.

11. In an electric fluid heater, a housing providing a fluid compartment and an aperture for fluid flow, an insulating liner for said fluid compartment having an opening communicating with said aperture, a metallic heating element disposed in said fluid compartment, a metallic shield positioned between said heating element and said opening in said liner, and means electrically connecting said shield with said heating element, whereby said shield is operative to protect said heating element from destructive electrolysis.

12. In an electric fluid heater, a housing providing a fluid compartment and a top aperture forfluid flow, an insulating liner for said fluid compartment having an opening communicating with said top aperture, a metallic heating element disposed in said fluid compartment with its midportion opposite said opening in said liner, a metallic shield positioned between said heating element and said opening in said liner, and means electrically connecting said shield with the midportion of said heating element, whereby said shield is operative to protect said heating element from destructive electrolysis.

13. In an electric fluid heater, an upright housing providing a fluid compartment and inlet and outlet apertures therefor, a portion of said fluid compartment having polygonal shaped side walls,

an insulating liner for said fluid compartment having a portion of its exterior surface conforming to and adapted to fit within said polygonal shaped walls and having openings communicating with said inlet and outlet apertures, an insulating base closing said fluid compartment, an insulating core projecting from said base within said fluid compartment, and a coiled heating element wound about said core.

onal section and having openings communicating with said inlet and outlet apertures, an insulating base closing said fluid compartment, an insulating core projecting from said base within said fluid compartment, and a coiled heating element Wound about said core.

RUSSELL U. STALEY.

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